Colored heat-resisting glass



UNITED STATES PATENT OFFICE WILLIAM G. TAYLOR, F CORNING, NEW YORK, ASSIGN'OR TO GORNING- GLASS WORKS OF CORNING, NEW YORK, A CORPORATION 015 NEW YORK COLORED HEAT-RESISTING GLASS Mo Drawing, Original application f lled June 12, 1925, Serial No. 36,737. Divided. and this application filed .Tune 10, 1926.

Commercial glasses having a linear expansion of .000005 or less per degree Centigrade are obtained by using large percentages of boric oxide, or low percentages of alkali combined with high silica contents. Glasses of this type are disclosed in the Sullivan & Taylor Patent 1,304,623. To color a glass of this; expansion'lhereafter designated low expansion glass) has been a problem in the in glass industry since the discovery of the low expansion glass itself. The ordinary glass coloring oxides when used in low expansion boro-silicate glasses seem to lose their characteristic absorption curves. For instance, cupr-ic oxide in a strongly basic glass shows a very high transmission of the green with slight transmission of yellow and blue and practically complete absorption of red, so that a good green basic glass can be obtained without undue absorption of light. In

strongly acidic glasses, such as the low expansion high boro-silicates, cupric oxide does not show suficient absorption of red and yellow to give a good green hue unless suificient coloring matteris added to absorb most of the light.

This characteristic is not confined to cupric oxide but is found to varying extents with all coloring oxides so that high transmission colors in low expansion boro-silicate glasses have been heretofore unobtainable, except in the case of reds and yellows produced by cadmium sulphide and selenium. These reds and yellows are diflicult to exactly control, because of change in hue and intensity due to melting conditions and heat treatment.

This invention is directed, therefore, to ob-,

taining a low expansion boro-silicate glass, which can be colored bythe usual coloring oxides, to obtain colors of the same nature as those obtainable with such oxides when used with basic glasses.

l[ have in my original application, Serial No. 36,737, filed June 12, 1925, of which this 5 is a division, generically claimed the subjectmatter above set forth, and have specifically claimed a blue glass specifically colored by cobalt oxide. The subject-matter of this application is directed therefore to obtaining a 59 low expansion boro-silicate glass which can Serial No. 115,13

be colored green by the usual coloring oxides, and specifically by oxide of copper, to obtain colors of the same nature as those obtainable by such oxide or oxides when used with basic glasses. T have discovered that a boro-silicate glass having these properties is possible if the following rules are observed, the purity of the color increasing as the glass conforms the more rigorously thereto.

1. Not only must the boric oxide content be small, but it must be low in molecular ratio to the alkali. High silica content with low alkali content, or high boric oxide percenta ge, does not affect the color of the oxides as seriously as high boric oxide content with low alkali content.

2. Lithia should be used as an alkali, both because of its fluxing power and its high combining power, as due to its low molecular weight lithia will combine with approximately twice as much boric oxide as will soda, and with approximately three times as much as will potash. Lithia unfortunately produces a decided tendency to crystallization with high silica. This tendency is reduced by alumina, boric oxide, and potash.

3. A small amount of alumina and potash should be present for reasons stated in the preceding paragraph. The amount of alumina that can be used is limited because of its marked effect in increasing hardness. Potash seems to be more useful than soda as its superiority in preventing crystallization more than ofisets its inferior fluxing power and molecular weight. llts use is limited by its fluxing power and effect on expansion.

In a more specific aspect, the invention consists in using from 1% to 3% of lithia for fluxing; an equal or greater amount of potash to prevent crystallization and improve color; about 1 to 3% alumina to prevent crystallization; apercentage of boric oxide depending on the amount of alkali used, the amount not to exceed twice the per cent of total alkali; and the balance silica and coloring oxides, the silica being over 79% of the base glass in order to obtain sufiiciently low expansion. The following is a typical glass embodying this invention which may be use as a base to which the desired oxides may be added for coloring SiO 82.6 B 0 8.8 K 0 3.4 Li O 3 A1 0 2.2

The linear expansion of this glass is between .0000035 and .0000040.

A satisfactory green is produced by the addition of 1.4% cupric oxide and .012% cobalt oxide to the base glass given above. Chromium or vanadium may be substituted in part for the cu'oric oxide.

A satisfactory yellow is produced by the addition of .25% nickel oxide, 2% maganese dioxide and .6% of uranium oxide.

A satisfactory blue with good absorption in other parts of the spectrum is produced by the addition of 1% cupric oxide and .1% cobalt oxide.

A very good yellow can be obtained by cerium and titanium or by various combina tions of nickel, maganese, cerium, uranium, titanium and iron oxides.

As an illustration of the effect of an apparently small change in composition, I state that glass B of the aforesaid Sullivan and Taylor patent destroys the desired coloring effects of the usual metallic oxides. That glass has the following composition:

s10 80.9% 13,0, 12.9 Na O 4.4 A1203 By usual coloring oxides I mean those metall1c oxldes commonly used in the art to produce colored silicates, these being listed on irilately the color which it produces in a basic ass.

g 2. A heat resisting green glass which shows high transmission of green light and generally good absorption of other parts of the spectrum, and which glass contains borlc oxide and lithia, the ratio of boric oxide to total alkali being less than 'two to one and which also contains cupric oxide.

3. A heat resisting green glass which shows high transmission of green light and genen ally good absorption of other parts of the spectrum, and which glass contams boric oxide and lithia, the ratio of boric oxide to total alkali being less than two to one and which also contains cupric oxide and cobalt oxide.

4. A heat resisting green glass which shows high transmission of green light and generally good absorption of other parts of the spectrum having a coefi'icient of linear expansion of less than .0000048, containing lithia, potash, and boric oxide, the ratio of boric oxide to total alkali being less than two to one.

' WILLIAM C. TAYLOR.

and iron. All of these, as before stated, re-

sult in a difierent color in commercial heat resisting glasses of high boric oxide content than in basic glasses. While it is true that the color due to uranium oxide does not vary with the two glasses to the same extent as do the colors of the other oxides above named, nevertheless the variations thereof are sufficient to bring it Withinthe general rule above stated.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

l. A heat resisting green glass which shows high transmission of green light and generally good absorption of other parts of the spectrum, andwhich glass contains boric oxide and lithia, the ratio of boric oxide to total alkali being less than two to one and which also contains a usual coloring oxide or oxides producing in the heat resisting glass approx- 

